This invention relates to extendable semi-trailers that can be lengthened or shortened to accommodate loads of varying lengths. More particularly, the invention relates to a mechanism and structure for accommodating the conduits that contain the electrical cables and hydraulic and pneumatic hoses as the length of the trailer is varied.
In order to supply the hydraulic or pneumatic brakes at the rear of the trailer and to provide electrical power for the required lights at the rear, the supply hoses and electrical cables must extend substantially the full length of the trailer. In semi-trailers where the trailer is a fixed length, this is not a problem, but where the length of a flat bed trailer can be varied to accommodate loads of varying lengths, the hoses and cables must be shortened and lengthened without interfering with the load. Typically, the hoses and cables must be detached and reattached, and some accommodation must be made for the extra length of the cables and hoses when the trailer is retracted. Also, these hoses and cables must be protected from damage and excessive wear, especially since failure in a brake line can be a serious safety hazard. In order to accommodate extension of the semi-trailer, the conduits containing the hoses and cables must be of sufficient length to service the rear of the semi-trailer when the trailer is fully extended, and these conduits must be supported, protected, and managed when the trailer is not extended.
The prior art reveals attempts at solving this problem. U.S. Pat. No. 4,103,931 discloses a system in which flexible, extendable cables support extendable, coiled conduits hanging below the bed of the semi-trailer. U.S. Pat. No. 3,165,336 discloses a system utilizing a cable and pulley system attached to springs wherein the extension of the springs and the positioning of the pulleys relative to one another accommodate the extension of the semi-trailer without requiring the use of extendable conduits. Though not directed to the problem inherent in extendable semi-trailers, U.S. Pat. No. 3,494,657 discloses the use of a protective metal channel to house the conduits as they extend along the length of the trailer from front to rear. However, none of these prior art solutions provide a simple, inexpensive way of completely managing and protecting the conduit and the hoses and cables it contains regardless of the length of the trailer. There is therefore a need for an improved means for supporting, guiding and protecting the conduit when the trailer is fully or partially extended or fully retracted.